Fuel Nozzle With Multiple Flow Divider Air Inlet

ABSTRACT

The present invention discloses a novel apparatus and way for directing a supply of compressed air into a fuel nozzle assembly for mixing with a fuel source. The apparatus comprises a fuel nozzle assembly having one or more coaxial flow dividers and radially-extending swirler vanes for directing a supply of fuel to a mixing tube. Compressed air is directed to flow in a primarily axial direction by passing through one or more coaxial flow dividers spaced axially and radially about the air inlet region of the fuel nozzle assembly so as to form a non-uniform radial distribution of compressed air to the inlet region of the fuel nozzle assembly.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

TECHNICAL FIELD

The present invention relates generally to an apparatus and method fordirecting a flow of compressed air into a fuel nozzle assembly. Morespecifically, a fuel nozzle assembly is provided with a flow directingdevice at an air inlet region.

BACKGROUND OF THE INVENTION

In an effort to reduce the amount of pollution emissions fromgas-powered turbine engines, governmental agencies have enacted numerousregulations requiring reductions in the amount of oxides of nitrogen(NOx) and carbon monoxide (CO) produced. Lower combustion emissions canoften be attributed to a more efficient combustion process, withspecific regard to fuel injector location, airflow rates, and mixingeffectiveness.

Early combustion systems utilized diffusion type nozzles, where fuel ismixed with air external to the fuel nozzle by diffusion, proximate theflame zone. Diffusion type nozzles historically produce relatively highemissions due to the fact that the fuel and air burn essentially uponinteraction, without mixing, and stoichiometrically at high temperatureto maintain adequate combustor stability and low combustion dynamics.

An enhancement in combustion technology is the concept of premixing fueland air prior to combustion to form a homogeneous mixture that burns ata lower temperature than a diffusion type flame and thereby produceslower NOx emissions. Premixing can occur either internal to the fuelnozzle assembly or external thereto, as long as it is upstream of thecombustion zone. An example of a premixing combustor has a plurality offuel nozzle assemblies, each injecting fuel into a premix chamber wherefuel mixes with compressed air from a plenum before entering acombustion chamber. Premixing fuel and air together before combustionallows for the fuel and air to form a more homogeneous mixture, which,when ignited will burn more completely, resulting in lower emissions.However, the thoroughness and completeness of the mixing and resultingburning of the fuel-air mixture depends on the effectiveness of themixing.

SUMMARY

The present invention discloses an apparatus and method for improvingthe air injection process for mixing with fuel injected through a fuelnozzle assembly. More specifically, in an embodiment of the presentinvention, a fuel nozzle assembly is disclosed comprising a plurality ofconcentric tubes forming first, second and third passageways. The fuelnozzle assembly also comprises a premix tube coaxial to and radiallyoutward of the third tube, the premix tube having a plurality of swirlervanes contained therein for inducing a swirl into a passing flow of airand fuel. The fuel nozzle assembly further comprises one or more coaxialflow dividers spaced axially and radially and extending around an inletend of the premix tube towards a base of the fuel nozzle. The one ormore coaxial flow dividers split and direct a passing airflow into thepremix tube of the fuel nozzle assembly.

In an alternate embodiment of the present invention, an air conditioningdevice for use in a fuel nozzle assembly is disclosed. The airconditioning device comprises a premix tube and one or more coaxial flowdividers positioned at an air inlet region of the fuel nozzle assembly.The one or more coaxial flow dividers each have a cylindrical portionand an air inlet portion that is turned radially outward from a centeraxis of the fuel nozzle assembly so as to form a plurality of annularair inlets, with the air inlets having unequal radial air flowdistributions.

In yet another embodiment of the present invention, a method ofconditioning an incoming air stream entering a fuel nozzle assembly isdisclosed. The method generally comprises providing a fuel nozzleassembly having one or more coaxial flow dividers positioned at the airinlet region of the fuel nozzle assembly. A flow of compressed air isprovided to the air inlet region and the coaxial flow dividers directthe compressed air through the areas formed between the coaxial flowdividers, where the areas formed generate a non-uniform radialdistribution of compressed air to the air inlet region of the fuelnozzle assembly.

Additional advantages and features of the present invention will be setforth in part in a description which follows, and in part will becomeapparent to those skilled in the art upon examination of the following,or may be learned from practice of the invention. The instant inventionwill now be described with particular reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The present invention is described in detail below with reference to theattached drawing figures, wherein:

FIG. 1 is a cross section of a fuel nozzle assembly in accordance withthe prior art.

FIG. 2 is a perspective view of a fuel nozzle assembly in accordancewith an embodiment of the present invention.

FIG. 3 is a cross section of the fuel nozzle assembly of FIG. 2 inaccordance with an embodiment of the present invention.

FIG. 4 is a perspective view of a portion of the fuel nozzle assembly inaccordance with an embodiment of the present invention.

FIG. 5 is a cross section view through the portion of the fuel nozzleassembly of FIG. 4 in accordance with an embodiment of the presentinvention.

FIG. 6 is an exploded view of the fuel nozzle assembly of FIG. 2 inaccordance with an embodiment of the present invention.

FIG. 7A is a perspective view of a fuel nozzle assembly in accordancewith an alternate embodiment of the present invention.

FIG. 7B is a cross section of the fuel nozzle assembly of FIG. 7A inaccordance with an alternate embodiment of the present invention.

FIG. 8A is a perspective view of a fuel nozzle assembly in accordancewith yet another alternate embodiment of the present invention.

FIG. 8B is a cross section of the fuel nozzle assembly of FIG. 8A inaccordance with yet another alternate embodiment of the presentinvention.

FIG. 9A is a perspective view of a fuel nozzle assembly in accordancewith a further alternate embodiment of the present invention.

FIG. 9B is a cross section of the fuel nozzle assembly of FIG. 9A inaccordance with a further alternate embodiment of the present invention.

FIG. 10 is a diagram depicting a method of conditioning an incomingairflow entering a fuel nozzle assembly in accordance with an embodimentof the present invention.

FIG. 11 is a cross section of an alternate embodiment of the fuel nozzleassembly of FIG. 2.

DETAILED DESCRIPTION

The present invention discloses a fuel nozzle assembly for use in a gasturbine combustion system for use in a premix combustion system to helpreduce emissions from the combustion system as shown in detail in FIGS.2-10. The fuel nozzle assembly as shown in FIGS. 2-9B is not to scalebut merely intended to represent the present invention. As one skilledin the art understands, a gas turbine engine typically incorporates aplurality of combustors. Generally, for the purpose of discussion, thegas turbine engine may include low emission combustors such as thosedisclosed herein and may be arranged in a can-annular configurationabout the gas turbine engine. One type of gas turbine engine (e.g.,heavy duty gas turbine engines) may be typically provided with, but notlimited to, six to eighteen individual combustors, each of them fittedwith the components outlined above. Accordingly, based on the type ofgas turbine engine, there may be several different fuel circuitsutilized for operating the gas turbine engine. Each combustor includesone or more fuel nozzle assemblies for supplying the fuel for generatingthe hot combustion gases.

Emissions from a combustion system are based in part on how completelythe fuel and air mix and then burn, or combust. In order to minimize theemissions and maximize the burning of the fuel that is being injected,it is preferable that the fuel and air are thoroughly mixed. To ensurethorough mixing, one factor considered is the condition of the airmixing with the fuel.

Referring initially to FIG. 1, a fuel nozzle assembly 100 of the priorart is shown in cross section. The fuel nozzle assembly 100 is similarto that of U.S. Pat. No. 6,438,961 assigned to the General Electric Co.The fuel nozzle assembly provides a swirler 102 for injecting fuel intoa passing air flow and an inlet flow conditioner 104 for directing theflow radially inward through a series of holes 106. The inlet flowconditioner 104 comprises a cylindrical wall portion and an end wallperpendicular to the cylindrical portion. The flow, is turned axiallythrough a plurality of turning vanes 108. However improved conditioningof the incoming airflow to the fuel nozzle assembly can be achievedthrough a simpler geometry.

An improved way of treating the incoming air flow to a fuel nozzleassembly is discussed below with respect to FIGS. 2-10. The fuel nozzleassembly 200 is in accordance with an embodiment of the invention. Morespecifically, referring to FIGS. 2 and 3, the fuel nozzle assembly 200comprises a first tube 202 extending along a center axis A-A and havinga first passageway 204 formed within the first tube 202. The firstpassageway 204, depending upon the operation of a combustion systemcontains a liquid, gas, air, or mixture thereof for purging the firstpassageway 204, where the contents of the first passageway 204 aredirected towards a tip region 205 of the fuel nozzle assembly 200.Depending on the configuration of the fuel nozzle assembly, the firsttube 202 can also include a blank or dual fuel cartridge extendingwithin the first tube 202 and along the center axis A-A that may bepurged with air. The cartridge, although not depicted, is sized to thenalso aid in establishing the correct size of the corresponding firstpassageway 204 for the gas or purge air.

Coaxial to and radially outward of the first tube 202 is a second tube206. A second passageway 208 is formed between the first tube 202 andthe second tube 206. The second passageway 208 extends coaxial to thefirst passageway 204 to within approximately swirler vanes 220, asdiscussed below. The second passageway 208 contains fuel, air, or amixture thereof directed to the swirler vanes 220, as discussed below.

The fuel nozzle assembly 200 also comprises a third tube 210 which iscoaxial to and radially outward of the second tube 206, thereby forminga third passageway between a portion of the second tube 206 and thethird tube 210 as well as between a portion of the first tube 202 andthe third tube 210. That is, the third passageway is split into twoportions, 212A and 212B, which do not communicate with each other. Afirst portion 212A extends from a base 224 of the fuel nozzle assembly200 to proximate the swirler vanes 220. A second portion 212B extendsfrom proximate the swirler vanes 220 to the tip region 205 of the fuelnozzle assembly 200. Through the first portion 212A flows a gas, wherethe gas initially travels axially through the first portion 212A andthen radially outward through the swirler vanes 220, where it isinjected into a surrounding air stream. The second portion 212B flowsair, gas, or a mixture thereof, which is drawn into the second portion212B at the region adjacent to the swirler vanes 220, through air inletholes 221. The air, fuel, or mixture thereof then passes axially throughthe second portion 212B to the tip region 205 of the fuel nozzleassembly 200, where it serves to mix with the liquid, air, gas, or amixture thereof from the first passageway 204 proximate the tip region205.

In an alternate embodiment of the present invention, a fuel-air mixturecan be provided to second portion 212B for injection through the tip ofthe fuel nozzle assembly. This is shown in FIGS. 3 and 6. The secondportion 212B can flow a gaseous fuel, air, or mixture thereof. In orderto supply second portion 212B with a flow of fuel, it is necessary forthe second portion 212B to be in fluid communication with the fuel-airmixture resulting from the plurality of swirler vanes 220. A fuelmixture can be supplied to the second portion 212B through one or moreholes 213 located in the third tube 210. The one or more holes 213 canbe oriented at an angle or perpendicular to the surface of the thirdtube 210.

Referring to FIG. 11, yet another alternate embodiment of the fuelnozzle assembly is depicted. As discussed above, second portion 212B canpass a fuel-air mixture to the tip region 205. However, this fuel can beprovided to second portion 212B through an alternate means, such asthrough holes 211 in the first tube 202. As such, fuel from firstpassageway 204 passes through holes 211 and into second portion 212B.

Referring back to FIG. 3, the fuel nozzle assembly 200 also comprises apremix tube 214 positioned coaxial to and radially outward of the thirdtube 210. The premix tube 214 has an inlet end 216 and an opposingoutlet end 218. A plurality of swirler vanes 220 extend radially betweenthe third tube 210 and premix tube 214. As it can be seen from FIGS.3-5, the inlet end 216 of the premix tube 214 has a flared edge directedgenerally radially outward from the center axis A-A. The plurality ofswirler vanes 220 are positioned about the center core of coaxial tubesof the fuel nozzle assembly 200 and provide a way of injecting andmixing fuel and air together to induce a swirl, as discussed furtherbelow.

The fuel nozzle assembly 200 also comprises one or more coaxial flowdividers 222 for dividing an incoming airflow stream, as shown in FIG.5. The exact quantity of coaxial flow dividers can vary, but for theembodiment of the present invention depicted in FIGS. 2-9, there are twocoaxial flow dividers, a first flow divider 222A and a second flowdivider 222B that work together with the inlet end 216 of the premixtube 214 and the base region 224 to split and direct the flow ofcompressed air into the fuel nozzle assembly 200. More specific featuresof the coaxial flow dividers 222 can be seen in FIGS. 4 and 5. Forexample, each coaxial flow divider 222 (and therefore 222A and 222B)include a cylindrical portion 226 having an axial length and an inletregion portion 228, where the inlet region portion 228 is turnedradially outward from the center axis A-A.

As discussed above, the one or more coaxial flow dividers direct asupply of compressed air into the fuel nozzle assembly 200. The coaxialflow dividers 222 are spaced apart in a radial and axial positioning tocreate a series of annular openings through which the air flows. Theeffective area of these openings, which regulates the amount of air thatcan pass therethrough, is controlled by this axial and radialpositioning of the coaxial flow dividers 222. More specifically, for theembodiment of the fuel nozzle assembly depicted in FIG. 3, there arethree air inlet areas generated by the plurality of coaxial flowdividers 222 and the premix tube 214. A first air inlet area 230 isformed between third tube 210/base 224 of the fuel nozzle assembly 200and the first flow divider 222A. A second air inlet area 232 is formedbetween the first flow divider 222A and the second flow divider 222B.Finally, for the embodiment depicted in FIG. 3, a third air inlet area234 is formed between the second flow divider 222B and the inlet end 216of the premix tube 214.

The series of air inlets 230, 232, and 234 form a series of co-annularflows of compressed air directed axially towards the plurality ofswirler vanes 220. However, the inlet areas 230, 232, and 234 to do notprovide a uniform radial air flow distribution due to the size of therespective openings. More specifically, the radial air flow distributionof the first air inlet 230 has a different radial air flow distributionthan that of the second air inlet 232. However, for one embodiment ofthe present invention, the radial air flow distribution of the first airinlet 230 is similar to that of the radial air flow distribution for thethird air inlet 234. Accordingly, for an embodiment of the presentinvention, the radial air flow distributions of the first air inlet 230and third air inlet 234 are each greater than the second air inlet area232. The one or more coaxial flow dividers 222 generate differentvolumes of air passing therethrough such that a greater amount of air isbiased to an inner diameter and outer diameter regions of the premixtube 214. For example, for one embodiment of the present invention, thesecond air inlet area 232 has a radial air flow distribution that isapproximately 85% of that of either the first air inlet area 230 orthird air inlet area 234. However, the air inlet areas may vary based ondownstream fuel input.

Another feature of the present invention is the ability to expand theair flow after it has passed through the one or more coaxial flowdividers 222 and corresponding air inlet areas (230, 232, and 234) andpasses through premix tube 214. In an embodiment of the inventiondepicted in FIGS. 3 and 5, the premix tube 214 tapers radially outwardat a region 215 to increase the volume within the premix tube 214. Assuch, the geometry of the premix tube 214 provides a way of expanding ordiffusing the compressed air immediately downstream of the second flowdivider 222B. The exact geometry of the premix tube and coaxial flowdividers may vary to avoid flow separation.

The overall shape of the coaxial flow dividers 222 and premix tube 214together provide a smooth way of transitioning the airflow into auniform axial flow direction. The shape and orientation of the one ormore coaxial flow dividers 222 provides a way to change the flowdirection of the compressed air while minimizing pressure loss. As oneskilled in the art understands, flow passing through a screen, such asthat of the prior art shown in FIG. 1 undergoes a pressure loss. Thepresent invention produces a slight squeeze to the compressed air andthen permits expansion of the compressed air to the desired geometry ofthe premix tube 214 and plurality of swirler vanes 220.

Referring to FIGS. 4 and 5, another feature of the present invention isa plurality of pins 240 positioned about and between the one or morecoaxial flow dividers 222. The plurality of pins 240 aid in holding theone or more coaxial flow dividers 222 together while also maintainingthe air inlet areas 230, 232, and 234 previously discussed. Theplurality of pins 240 are secured to the one or more coaxial flowdividers 222 by a means such as welding or brazing. As such, the pinsare generally fabricated from a material similar in thermal andmechanical properties to that of the one or more coaxial flow dividers222.

Alternate embodiments of the present invention are depicted in FIGS.7A-9D. Generally speaking, these alternate embodiments provideadditional ways of securing the one or more coaxial flow dividers to thefuel nozzle assembly while also maintaining the air inlet areaspreviously discussed. Referring initially to FIGS. 7A and 7B, a fuelnozzle assembly 700 is disclosed, which is generally similar instructure and operation to the fuel nozzle assembly of FIGS. 2-6. Thefuel nozzle assembly 700 includes a premix tube 714, one or more coaxialflow dividers 722 and a plurality of pins 740. To enhance the structuralrigidity of the fuel nozzle assembly 700 and the one or more coaxialflow dividers 722, a plurality of struts 742 are positioned extendingbetween and secured to the one or more coaxial flow dividers 722 at theradially outermost point and the inlet end 716 of the premix tube 714.The plurality of struts 742 are secured to the one or more coaxial flowdividers 722 and premix tube 714 by a means such as welding or brazing.The exact size, quantity and spacing of the plurality of struts 742 willvary depending on a number of factors such as the size and number ofcoaxial flow dividers 722 and size of the air inlet areas.

An alternate embodiment of the fuel nozzle assembly having improvedstructural integrity at the air inlet region is shown in FIGS. 8A and8B. A fuel nozzle assembly 800 is depicted in FIGS. 8A and 8B, and isgenerally similar in structure and operation to the fuel nozzle assembly200 of FIGS. 2-6. The fuel nozzle assembly 800 includes a premix tube814, one or more coaxial flow dividers 822 and a plurality of pins 840.To enhance the structural rigidity of the fuel nozzle assembly 800 andthe one or more coaxial flow dividers 822, a plurality of struts 842extend across the edge or inlet region of each of the coaxial flowdividers 822, where the plurality of struts 842 are secured to the oneor more coaxial flow dividers 822 and the inlet end 816 of the premixtube 814. The plurality of struts 842 are secured to the coaxial flowdividers 822 and premix tube 814 preferably by a weld or braze. Theexact size, quantity and spacing of the plurality of struts 842 willvary depending on a number of factors such as the size and number ofcoaxial flow dividers 822 and size of the air inlet areas.

A further alternate embodiment of the present invention is depicted inFIGS. 9A and 9B. This embodiment also provides a way of improving thestructural integrity at the air inlet of the fuel nozzle assembly. Afuel nozzle assembly 900 is depicted in FIGS. 9A and 9B, and isgenerally similar in structure and operation to the fuel nozzle assembly200 of FIGS. 2-6. The fuel nozzle assembly 900 includes a premix tube914, one or more coaxial flow dividers 922 and a plurality of pins 940.To enhance the structural rigidity of the fuel nozzle assembly 900 andthe one or more coaxial flow dividers 922, a plurality of struts 942extend through a portion of the flow dividers 922 and a portion of thepremix tube 914. The plurality of struts 942 extend through the coaxialflow dividers 922 by passing through one or more holes in the flowdividers 922. The coaxial flow dividers 922 are then secured to the oneor more coaxial flow dividers 922 and the inlet end 916 of the premixtube 914 by a means such as brazing or welding. The exact size, quantityand spacing of the plurality of struts 942 will vary depending on anumber of factors such as the size and number of coaxial flow dividers922 and size of the air inlet areas.

Referring now to FIG. 10, another embodiment of the present invention isdisclosed. A method 1000 of conditioning an incoming air stream enteringa fuel nozzle assembly is disclosed. In a step 1002, a fuel nozzleassembly is provided having one or more coaxial flow dividers positionedat an air inlet region of the fuel nozzle assembly with the coaxial flowdividers spaced axially and radially at the air inlet region. Thespacing of the coaxial flow dividers creates a plurality of areas. In astep 1004, a flow of compressed air is provided to the air inlet regionof the fuel nozzle assembly. Once the flow of compressed air isprovided, in a step 1006, the compressed air is directed through each ofthe plurality of areas formed by the coaxial flow dividers with the airflowing in a direction that is coaxial to a center axis. The coaxialflow dividers are spaced and oriented so as to provide a non-uniformradial distribution of compressed air to the inlet region of the fuelnozzle assembly. Upon exit from the coaxial flow divider region, thecompressed air is oriented in primarily an axial direction.

While the invention has been described in what is known as presently thepreferred embodiment, it is to be understood that the invention is notto be limited to the disclosed embodiment but, on the contrary, isintended to cover various modifications and equivalent arrangementswithin the scope of the following claims. The present invention has beendescribed in relation to particular embodiments, which are intended inall respects to be illustrative rather than restrictive.

From the foregoing, it will be seen that this invention is one welladapted to attain all the ends and objects set forth above, togetherwith other advantages which are obvious and inherent to the system andmethod. It will be understood that certain features and sub-combinationsare of utility and may be employed without reference to other featuresand sub-combinations. This is contemplated by and within the scope ofthe claims.

1. A fuel nozzle assembly comprising: a first tube extending along acenter axis and having a first passageway therein; a second tube coaxialto and radially outward of the first tube and forming a secondpassageway between the first tube and the second tube; a third tubecoaxial to and radially outward of the second tube and forming a thirdpassageway between the second tube and a portion of the third tube and aportion of the first tube and the third tube; a premix tube coaxial toand radially outward of the third tube, the premix tube having an inletend and an opposing outlet end, the premix tube having a plurality ofswirler vanes positioned between the third tube and premix tube, theplurality of swirler vanes configured to inject fuel and induce a swirlinto a passing flow of fuel and air; and, one or more coaxial flowdividers, each of the coaxial flow dividers having a cylindrical portionand an inlet region portion, where the inlet region portion is turnedradially outward from the center axis; wherein the one or more coaxialflow dividers split and direct a passing airflow into the premix tube.2. The fuel nozzle assembly of claim 1, wherein the first tube containsa cartridge for supplying purge through a first passageway.
 3. The fuelnozzle assembly of claim 2, wherein the first passageway contains eitherliquid, gas, air, or a mixture thereof.
 4. The fuel nozzle assembly ofclaim 3, wherein the second passageway contains air, fuel, or a mixturethereof.
 5. The fuel nozzle assembly of claim 4, wherein the thirdpassageway is divided into a first portion and a second portion, thefirst portion extending from proximate a base of the fuel nozzleassembly to proximate the plurality of swirler vanes, while the secondportion extends from proximate the plurality of swirler vanes toproximate a tip region of the fuel nozzle assembly, where the firstportion is not in fluid communication with the second portion.
 6. Thefuel nozzle assembly of claim 5, wherein the first portion of the thirdpassageway contains gas and the second portion of the third passagewaycontains air, gas, or a mixture thereof.
 7. The fuel nozzle assembly ofclaim 1, wherein the inlet end of the premix tube tapers radiallyoutward from the center axis.
 8. The fuel nozzle assembly of claim 1,further comprising a plurality of struts extending between and securedto the one or more coaxial flow dividers and the premix tube.
 9. Thefuel nozzle assembly of claim 8, wherein the plurality of struts extendthrough a portion of the coaxial flow dividers and a portion of thepremix tube.
 10. The fuel nozzle assembly of claim 8, wherein theplurality of struts extend across the inlet region of each of thecoaxial flow dividers.
 11. An air conditioning flow device for use in afuel nozzle assembly comprising: a premix tube having an inlet endturned radially outward from a center axis of the fuel nozzle assembly;and, one or more coaxial flow dividers positioned at an air inlet regionof the fuel nozzle assembly, each coaxial flow divider having acylindrical portion extending an axial length and an air inlet portionturned radially outward, the one or more coaxial flow dividers spacedaxially and radially so as to form a plurality of annular air inletareas therebetween, so as to form an unequal radial air flowdistribution between the coaxial flow dividers.
 12. The air conditioningflow device of claim 11, wherein the plurality of coaxial flow dividerscomprise a first and second flow divider.
 13. The air conditioning flowdevice of claim 12, wherein a first air inlet area is formed between athird tube of the fuel nozzle assembly and the first flow divider, asecond air inlet flow area is formed between the first and second flowdividers, and a third air inlet area is formed between the second flowdivider and the inlet end of the premix tube.
 14. The air conditioningflow device of claim 13, wherein the first air inlet area has adifferent radial air flow distribution than the second air inlet area.15. The air conditioning flow device of claim 14, wherein the first airinlet area has a similar radial air flow distribution to the third airinlet area.
 16. The air conditioning flow device of claim 15, whereinthe first air inlet area and third air inlet area each have a radial airflow distribution that is greater than the second air inlet area. 17.The air conditioning flow device of claim 13 further comprising aplurality of struts extending between and secured to the one or morecoaxial flow dividers and the premix tube.
 18. A method of conditioningan incoming air stream entering a fuel nozzle assembly comprising:providing the fuel nozzle assembly having one or more coaxial flowdividers positioned at an air inlet region of the fuel nozzle assemblyand spaced axially and radially at the air inlet region; providing aflow of compressed air to the air inlet region of the fuel nozzleassembly; and, directing the compressed air through each of a pluralityof areas formed by the one or more coaxial flow dividers and in adirection coaxial to a center axis of the fuel nozzle assembly; whereinthe plurality of areas provide a non-uniform radial distribution ofcompressed air to the air inlet region of the fuel nozzle assembly. 19.The method of claim 18, wherein the coaxial flow dividers furthercomprise a plurality of radially extending support pins positionedradially between adjacent coaxial flow dividers.
 20. The method of claim18, wherein the compressed air is oriented in primarily an axialdirection upon exiting the coaxial flow dividers and entering the premixtube of the fuel nozzle assembly.